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Computer-Assisted Knee Replacement - - A new technology for precision

  
  April 25, 2008  
  By Robert Tennant, MD Orthopedic Surgeon  
     
  For the patient who suffers from knee arthritis, there is a new technology for performing knee replacement surgery. Computer-assisted knee replacement surgery guides the surgeon through the case, resulting in more precise cuts and alignment of the knee implants. This will lessen the chance of “loosening” of the joint implant and provide a more predictably successful outcome. Previous methods of knee replacement surgery could create “outliers” of patients whose mal-alignment (poor leg alignment) would result in increased wear of the replaced joint. Patients with only half the knee affected by arthritis may be a candidate for a unicondylar (half) knee replacement.  
     
  I became interested in computer-assisted surgery in 2004 as patient demand for new technology and minimally invasive procedures started to grow. So I decided to train on the computer-assisted system because it provides real-time, three-dimensional images of the individual patient’s anatomy. As a result, I am able to clearly view the bone structure and the detailed data provided by the computer system to assist with the precise alignment of the implants.  
 
     
 

About Computer Assisted Knee Surgery:

 
     
  Computer-assisted knee replacement surgery enables surgeons to operate with smaller incisions and greater precision. Computer-assisted surgery helps surgeons align the patient's bones and knee replacement implants with a degree of accuracy not possible with the naked eye. For the first time, doctors have detailed information allowing them to balance the ligaments and it is given to them before they make the necessary cuts. Computers also help the doctor use smaller incisions instead of the traditional larger openings. Small-incision surgery, most often referred to as minimally invasive surgery, offers the potential for faster recovery, less bleeding, and less pain for patients.  
     
  Think of it this way. Perhaps you've seen the on-board computers in newer cars that provide driving directions using satellite navigation systems. On-board computers collect data points from satellites and use precise coordinates to give drivers directions from point A to point B. It provides a degree of precision, speed and accuracy not attainable with a map and compass.
Similarly, computers used during orthopaedic surgeries offer visual mapping to help the doctor make crucial decisions before and throughout the knee replacement operation. The objective is to combine the precision and accuracy of computer technology with the surgeon's skill to perform surgery.
An advantage is that the doctor has greater "vision" when it counts — during surgery. This supports decision-making and enhances the surgeon's flexibility.

 
 

Here's how it works. Computer-assisted surgery uses:


• the computer system
• cameras
• software
• specialized surgical instruments
• physician training

 
   
     
 

The software and instrumentation are designed to work together. Imaging technology allows the surgeon to see a computer generated picture representation of a patient's knee joint allowing them the potential to operate with smaller openings and with more precision.

The Computer System is a lightweight, wireless computer that is used with a small camera array. A digital model is produced that serves as a map for each operation. The cameras take data via infrared signals from reflectors placed on the patient's body and on specially designed surgical instruments. The computer uses the data to track the exact position of the patient and the instruments on a monitor. The combination of computer visualization and special surgical instruments allows the doctor to align the knee replacement implant with greater precision than when doing the procedure with the naked eye. Advocates of the technology say they expect the use of computer-aided surgery to spread rapidly in the next decade because of the following potential benefits:

  • support for the doctor in pre-operative planning
  • intra-operative flexibility to adapt the plan based on the data shown during the surgery
  • improved surgical accuracy and consistency
The future of computer-assisted surgery is exciting and promising. Total joint replacement is a proven procedure that has been successful for decades in helping people live with less pain and greater mobility. 		 
     
 

Rotating Platform Knee Replacement

 
     
 

Advanced technologies are revolutionizing knee replacements. Rotating Platform Knees, a type of Mobile-Bearing Knee, are unique because they are designed to accommodate normal movement while minimizing implant wear, when compared to traditional knee replacements.

The difference between a rotating platform knee implant and the more traditional fixed bearing implant is the range of movement — the fixed bearing implant can only flex and extend (called articulation) while the rotating platform knee implants move almost like a normal knee joint. They allow the knee to twist and turn (rotation) as well as flex and extend.

In addition to allowing more normal movement, the rotating platform implant spreads the contact between the upper and lower parts more evenly, reducing the stress of everyday activities on the implant. The rotation of the bearing insert also takes pressure off the areas where the bone and the implant come together — potentially increasing the longevity of the implant and reducing the risk that the implant will loosen over time. 		 
     
 

Rotating Platform Knee Options

 
     
  There are two different Rotating Platform knee systems: Sigma RP Knee System and the Sigma RP-F Knee System.  
 

Sigma RP Knee System

The Rotating Platform Knee replacement system implant allows the knee to bend and rotate, move back and forth, and flex and extend.
It is designed to accommodate normal movement and to meet your body's need for a more normal rotation.

   
     
 
Sigma RP-F Knee System

Much like the other Rotating Platform Knee replacement system where the implant allows the knee to bend and rotate, move back and forth, and flex and extend, the Sigma RP-F also allows for deep knee flexion. Deep knee flexion is the movement needed for kneeling, squatting or sitting cross-legged. It may allow you to participate in social, cultural, religious or leisure activities that are important to you. 		   
     
 

Rotating Platform Knee Technology: What You Should Know

 
     
 
  • Rotating Platform (Mobile-Bearing) Knee replacements bring technological advancement to a proven design in knee implants. The Rotating Platform Knee is designed to bend and rotate, move back and forth, flex and extend, helping to accommodate more normal movement.
  • Rotation is important because it may prolong the life of the implant by putting less stress on the knee, reducing the chance of it wearing out over time.
  • Some people may think it's better to delay surgery until they're older because they believe that knee implants don't last. Rotating Platform Knees are designed for patients who want their knee replacement to accommodate normal movement while significantly minimizing implant wear (as compared to traditional knees). Minimizing implant wear can help your knee replacement last longer.
  • Women may be especially interested in this technology since their knees rotate more than those of a man during normal movement. The Rotating Platform Knee accommodates for this.
 
     
 
 
   
     
 
Rotating Platform Traditional Fixed Bearing
 
     
 
 
     
 

The difference between a rotating platform knee implant and the more traditional fixed bearing implant is the range of movement — the fixed bearing implant can only flex and extend (called articulation) while the rotating platform knee implants move almost like a normal knee joint. They allow the knee to twist and turn (rotation) as well as flex and extend.